Streptozotocin-induced Diabetic Nephropathy In Rats Research Articles

Novel biphenyl compound, VMNS2e, ameliorates streptozotocin‐induced diabetic nephropathy in rats

To study the effect of a new biphenyl synthetic compound showing interactions with the active site of protein tyrosine phosphatase 1B by docking and molecular dynamics, VMNS2e in streptozotocin-induced diabetic nephropathy in rats with various renal function parameters and renal ultrastructure. Streptozotocin (55 mg/kg)-induced diabetic rats were orally treated once daily with VMNS2e (30, 60, and 120 mg/kg) for 8 weeks. The body weight and blood glucose levels of the rats were recorded during the study period. After 8 weeks of treatment creatinine clearance, urinary protein, blood urea nitrogen, urinary albumin excretion rate, and insulin levels were measured. An ultrastructure study of the kidney tissue was performed and the glomerular basement membrane thickness was measured. Eight weeks of VMNS2e treatment significantly reduced the fasting blood glucose level, attenuated elevating blood urea nitrogen levels, and reduced glomerular basement membrane thickness. It is concluded that VMNS2e treatment at 30 and 60 mg/kg, when given for 8 weeks, partly ameliorated early diabetic nephropathy in diabetic rats.

Effects of Tangshenping Capsule on the Renal Protection and Expressions of TGF-β1 and mRNA in Streptozotocin induced Diabetic Nephropathy Rats

Abstract This work aimed to observe the effects of “Tangshenping Capsule” on the renal protection and expressions of TGF-β1 protein and mRNA in streptozotocin-induced diabetic nephropathy (DN) rats. 50 SD rats were randomly divided into the normal control group (n=10) and the model group (n= 40). 55 mg/kg one-time intraperitoneal injection of streptozotocin was used to induce diabetes model rats. 72 hours after injection, rats with blood glucose higher than 16.7 mmol/L and urinary glucose higher than 4+, were selected as diabetes rats. Then those modeling success rats were re-randomized into the model group, the irbesartan group and the Tangshenping capsule group. Body weight was weighed every week, 24 h divla cage urine was collected at week 4, 8 and 12 after streptozotocin injection, and 24 h urine protein was detected. All rats were sacrificed after 12 weeks treatment. Blood urea nitrogen (BUN), serum creatinine (Scr), and triglyceride (TG) were detected in blood serum. Pathological changes of renal tissue were observed by Mallory staining, TGF-β1 protein and mRNA expression of the renal tissue were detected by immunohistochemistry and in situ hybridization. Rats of the model groups had different levels of feeding and sleeplessness, slow activity, weight loss, 24 h urinary protein increase, and abnormal blood biochemical indicators, while the rats from the irbesartan and the Tangshenping capsule group were all improved in different degrees in the above aspects, and the Tangshenping capsule group was superior to the irbesartan group; the model group showed obvious DN pathological renal changes; in the normal group and the treatment groups, renal tubular epithelial cells and interstitial cells had mild TGF-β1 and mRNA expression, while there was strong expression in the model group. The TGF-β1 and mRNA expression in the Tangshenping capsule group was significantly reduced (P

Zhen-wu-tang, a blended traditional Chinese herbal medicine, ameliorates proteinuria and renal damage of streptozotocin-induced diabetic nephropathy in rats

Ethnopharmacological relevance Zhen-wu-tang (ZWT) is a blended traditional Chinese medicine specifically used for various kidney diseases. Aim of the study The present study is to evaluate the effects of ZWT on diabetic nephropathy and investigate the potential anti-diabetic mechanisms. Materials and methods Streptozotocin (STZ)-induced diabetic rats were orally administrated ZWT (80,320 mg/kg b.w.) once a day, for a period of 12 weeks. Body weight, urinary volume, urine protein and blood biochemical parameters were measured every 3 weeks. At the end of the observation period, kidneys were isolated for histology, angiotensin II content determination, real time PCR and Western blot analyses. Results ZWT (320 mg/kg b.w.) prevented body weight loss, reduced polyurea, urinary protein excretion, serum creatinine and blood urea nitrogen, although it did not alter the hyperglycemia. It ameliorated glomerular hypertrophy and expansion of the mesangial area, swell and effacement of foot process. It also suppressed the increased expression of angiotensin II, nephrin and podocin. Conclusions Data from this study suggest that ZWT possess a protective effect on renal damage of STZ-induced diabetic nephropathy in rats, by suppressing hyperactivity of renal renin–angiotensin system that turns in to modulate renal nephrin and podocin expressions, thereby protecting podocyte from injury.

Silymarin and milk thistle extract may prevent the progression of diabetic nephropathy in streptozotocin-induced diabetic rats

Objectives: To investigate the effect of silymarin and milk thistle extract on the progression of diabetic nephropathy (DN) in rats. Methods: Diabetes was induced with a single intraperitoneal (IP) injection of streptozotocin (STZ) (60 mg/kg). Silymarin (100 mg/kg/d) or the extract (1.2 g/kg/d) was gavaged for 4 weeks. Blood glucose (BS), serum urea (Su), serum creatinine (Scr), and 24-h urine protein (Up) were measured and glomerular filtration rate (GFR) was calculated. Concentration of thiobarbituric acid reactive species (TBARS) and activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) were evaluated in the renal tissue. Results: Data were expressed as mean ± SEM. Silymarin or the extract had no significant effect on BS, Scr, and GFR. Both milk thistle extract and silymarin, respectively, decreased Su (mg/dL) (87.1 ± 7.78, p < 0.001; 84.5 ± 7.15, p < 0.001), Up (mg) (5.22 ± 1.56, p = 0.014; 5.67 ± 0.86, p = 0.034), and tissue TBARS (nmol/mg protein) (0.67 ± 0.04, p < 0.001; 0.63 ± 0.07, p < 0.001) in diabetic rats, compared to diabetic control (DC) (Su: 131.0 ± 4.55, Up: 8.3 ± 0.84, TBARS: 0.94 ± 0.06). Both the extract and silymarin could increase the activity of CAT (IU/mg protein) (25.5 ± 4.0, p = 0.005; 20 ± 1.8, p = 0.16) and GPx (IU/mg protein) (0.86 ± 0.05, p = 0.005; 0.74 ± 0.04, p = 0.10), respectively, in diabetic rats compared to DC (CAT = 14.4 ± 2.0, GPx = 0.57 ± 0.02). Conclusion: Milk thistle extract, to a lesser extent silymarin, can attenuate DN in rats possibly by increasing kidney CAT and GPx activity and decreasing lipid peroxidation in renal tissue.

Dietary polyunsaturated fatty acids slow the progression of diabetic nephropathy in streptozotocin-induced diabetic rats

Diabetic nephropathy is associated with lipid deposits in the kidney. We hypothesized that a diet containing polyunsaturated fatty acids (PUFAs) could ameliorate pathogenesis of diabetic kidney diseases associated with lipid depositions in the kidneys. We examined if the pathogenesis and progression of diabetic nephropathy are affected by the type of dietary fat using streptozotocin (45 mg/kg body weight, intravenous)-induced diabetic rats (5-week-old male Sprague-Dawley rats). Streptozotocin-induced diabetic rats were fed a lard diet containing saturated fatty acids or a rapeseed oil diet containing PUFAs (DML and DMR, respectively) for 11 days. Similarly, streptozotocin-nontreated rats were fed a lard diet or a rapeseed oil diet (NL and NR, respectively) for 11 days. Hyperglycemia was induced in DML and DMR, compared with NL and NR groups. The levels of plasma ketone, total cholesterol, and triglyceride (TG) were significantly increased in the DML group. Moreover, albuminuria and renal TG content were enhanced in the DML group. The renal TG content correlated positively with urinary albumin excretion (P < .001). Oil-Red O staining of kidney sections indicated a marked accumulation of neutral lipids in both glomerular and tubular cells in the DML group. In addition, a renal sterol regulatory element-binding protein-1 mature protein increment was induced in the DML group. Conversely, sterol regulatory element-binding protein-1 expression in the kidney was maintained at normal levels in the DMR group. These results suggest that dietary PUFAs may slow the progression of diabetic nephropathy associated with lipid depositions in the kidney.

Ameliorative potential of angiotensin1-7/Mas receptor axis in streptozotocin-induced diabetic nephropathy in rats

The present study was designed to investigate the effects of angiotensin(1-7) (Ang(1-7)) a Mas receptor agonist, and A-779, a Mas receptor antagonist, in streptozotocin-induced diabetic nephropathy (DN). A single administration of streptozotocin (STZ) (50 mg/kg i.p.) to rats produced diabetes, and diabetic nephropathy developed after 8 weeks of STZ administration. The extent of DN was assessed biochemically and morphologically by measuring serum creatinine, creatinine clearance, blood urea nitrogen (BUN), proteinuria, urinary N-acetyl-beta-D glucosaminadase activity, renal collagen contents, lipid profile, serum nitrite/nitrate concentration and kidney weight/body weight (%). Treatments with Ang(1-7) (576 microg/kg/day i.p. for 4 weeks) and Ang(1-7) plus A-779 (744 microg/kg/day i.p. for 4 weeks) were started after 4 weeks of STZ administration. The treatment with Ang(1-7) attenuated STZ-induced nephropathy in rats by decreasing proteinuria, renal collagen content and by improving endothelial functions without preventing tubular damage. It has been shown for the first time that treatment with Ang(1-7) decreases dyslipidemia and BUN in diabetic rats, implying a renoprotective effect of the peptide. However, serum creatinine, creatinine clearance and kidney weight/body weight (%) remained unaffected with Ang(1-7) treatment. It may be concluded that activation by specific agonists of the Mas receptor may be useful in combating glomerular damage in DN.

Beneficial effects of Phellodendri Cortex extract on hyperglycemia and diabetic nephropathy in streptozotocin-induced diabetic rats

This study investigated the effect of Phellodendri Cortex extract on hyperglycemia and diabetic nephropathy in streptozotocin-induced diabetic rats. Male Sprague-Dawley rats were divided into normal control (NC), diabetic control (DC), and diabetic treatment with Phellodendri Cortex extract (DP). Over a 4-week experimental period, Phellodendri Cortex extract was administered orally at 379 mg/kg BW/day. The final fasting serum glucose level, urine total protein level, and relative left kidney weight in the DP group were significantly lower than the DC group. Renal XO and SOD activities in the DP group were significantly lower than the DC group and renal CAT activity in the DP group was significantly higher than the DC group. Tubular epithelial change was reduced in the DP group compared to the DC group. These results indicated that Phellodendri Cortex can reduce glucose level and prevent or retard the development of diabetic nephropathy in streptozotocin-induced diabetic rats.

Effect of Picrorrhiza Rhizoma Extracts on Early Diabetic Nephropathy in Streptozotocin-Induced Diabetic Rats

The hypoglycemic effect of an aqueous extract of Picrorrhiza Rhizoma (PR) was investigated on diabetic nephropathy. The body weight of each of eight rats per group was measured 7 days after streptozotocin (STZ) treatment. The blood glucose levels 3 days after STZ treatment and the changes in body weight, kidney weight, blood glucose levels, and serum blood urea nitrogen (BUN) were also measured, and the histopathology of the kidney was examined. Body weight decreases and increases of kidney weight, blood glucose levels, and serum BUN and creatinine levels were detected in the diabetic control with histopathological changes related to diabetic nephropathy in the kidney. However, the level of hyperglycemia was significantly lowered in all groups given the PR extract. In addition, the changes related to diabetic nephropathy with the body weight were also significantly lower in the captopril and all PR extract-dosing groups than in the diabetic control. In conclusion, an aqueous extract of PR has relatively good inhibitory effects on STZ-induced diabetes with early diabetic nephropathy with a similar efficacy to an equal dose of captopril.

L-Arginine Attenuates Diabetic Nephropathy In Streptozotocin-Induced Diabetic Rats

Oxidative stress is widely recognized as a key component in the development and progression of diabetic complications, such as diabetic nephropathy (DN). The present study aimed to evaluate the efficacy of dietary L-arginine supplementation as a potentially novel and useful strategy for the management of oxidative stress implicated in diabetic nephropathy. Control rats, streptozotocin(STZ)-induced diabetic rats, and STZ-induced diabetic rats treated with L-arginine (1.51%)in drinking water were sacrificed after 4 weeks. Results have shown that L-arginine was able to ameliorate the oxidative stress imposed by diabetes as reflected by the significant decrease in elevated plasma glucose, glycated hemoglobin (HbA1C), and renal malondialdehyde(MDA)level and glutathione-S-transferase(GST) activity. In addition, significant increase in reduced activities of plasma lactate dehydrogenase(LDH) and renal glutathione reductase(GR) were observed. On the other hand, no significant change was detected in body weight, kidney weight and relative kidney weight, levels of plasma fructosamine, MDA and NOx, renal activities of glutathione peroxidase(GPx),superoxide dismutase(SOD), LDH, aldose reductase(AR),sorbitol dehydrogenase(SDH), levels of renal glutathione(GSH) and NOx in the diabetic group treated with L-arginine. It can be concluded that L-arginine supplementation may become a promising solution to reduce lipid peroxidation and improve associated complications in diabetes. Keywords: Diabetic nephropathy- L-arginine- Reactive oxygen species-Malondialdehyde-Nitric oxide-Rat. Egyptian Journal of Biochemistry and Molecular Biology Vol. 26 (1) 2008 pp. 1-22

Effect of compound Puerarin on the collage IV in streptozotocin-induced diabetic nephropathy rats

To observe the effect of compound Puerarin on collagen IV of streptozotocin-induced diabetic rats. Diabetic nephropathy rats were induced by intraperitoneal injection of streptozotocin (STZ). Rats were allocated randomly to control group (10), diabetes model group (10), Vitamin C group (10), Puerarin group (10), vitamin C plus Puerarin group (10). The study period lasted for 12 weeks. During and after the treatment, the general state, blood glucose levels, glycosylated hemoglobin, blood urea nitrogen, serum collagen IV, blood urea nitrogen, serum creatinine, urinary albumin excretion rate of the 24-hour, and clearance rate of creatinine collagen IV protein were determined by immunohistochemistoche analysis as well as type the gene expression of collagen IV alpha 1 mRNA were determined by in situ hybridization analysis in the kidney tissue of different groups. (1) Diabetes mellitus and renal function lesion occurred in the four groups. (2) Vitamin C and Puerarin could improve the general conditions of diabetic Rats, decrease blood urea nitrogen [(8.68 +/- 0.43), (7.98 +/- 0.47) and (5.76 +/- 0.82) micromol/L, serum creatinine [(74.68 +/- 8.20), (75.52 +/- 7.98) and (58.66 +/- 6.65) mmol/L], and urinary albumin excretion rate of the 24-hour [(18.40 +/- 0.37), (17.24 +/- 0.30) and (9.97 +/- 1.27) mg/24 h x 10(-3)]; increase clearance rate of creatinine [(0.59 +/- 0.21), (0.61 +/- 0.14) and (0.69 +/- 0.32) ml/min], the expression of collage IV absorbance [(111.56 +/- 14.61), (110.78 +/- 9.69) and (95.44 +/- 9.97) ] in the diabetic Rats were significantly inhibited at the same time. The compound Puerarin might have some functions on preventing ren by inhibiting expression of type IV collagen.

Dietary nitrite inhibits early glomerular injury in streptozotocin-induced diabetic nephropathy in rats

Increased production of reactive oxygen species (ROS) is a key event leading to microvascular complications, including nephropathy, in diabetes mellitus (DM). Excessive ROS and oxidative stress in DM have been reported to be associated with subsequent impaired nitric oxide (NO) bioavailability. The aim of this study is to examine the beneficial function of dietary nitrite supplementation as an interventional NO donor to attenuate early progression of diabetic nephropathy. To test this hypothesis, male Sprague–Dawley rats were randomly divided into four groups: non-diabetic rats given water with or without nitrite (nitrite-treated or untreated, respectively), and streptozotocin-induced diabetic rats given water with or without nitrite (nitrite-treated or untreated, respectively). After a 4 week experimental period, untreated diabetic rats exhibited significantly higher malondialdehyde (MDA) levels in the kidney compared with untreated non-diabetic rats, accompanied by a reduction in levels of endogenous NO synthase-derived nitrite. However, dietary nitrite supplementation to diabetic rats not only decreased MDA levels but also increased nitrite levels in the kidney to the same levels as in the non-diabetic kidney. These improvements accompanied an improvement in the parameters of glomerular injury, including urinary protein and albumin excretion, histopathological glomerular hypertrophy, and mesangial matrix accumulation. These results indicate that dietary nitrite is effective in the prevention of early diabetic glomerular injury in which NO bioavailability is impaired.

The Rho-kinase inhibitor, fasudil, attenuates diabetic nephropathy in streptozotocin-induced diabetic rats

This study aimed to investigate the effect of the Rho-kinase inhibitor fasudil on the development of diabetic nephropathy and clarify a contribution of the Rho/Rho-kinase pathway to the pathogenesis of diabetic nephropathy. Diabetes was induced in male Sprague–Dawley rats with an intraperitoneal injection of streptozotocin. Animals were then divided into the following 4 groups; normal control rats, diabetic rats, diabetic rats administered fasudil orally and diabetic rats administered fluvastatin (3-hydroxy-methylglutaryl coenzyme A reductase inhibitor, statin) orally. After 1 month of treatment, neither fasudil nor statin had any influence on blood glucose or blood pressure in diabetic rats . While urinary excretion of albumin and 8-hydroxydeoxyguanosine (8-OHdG) was increased in diabetic rats, both of these increases were abolished by fasudil and statin. Rho activity was enhanced in the renal cortex of diabetic rats compared to normal controls, and this enhancement was abolished by statin treatment. Expression of transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) mRNA was up-regulated in the renal cortex of diabetic rats, and this was abolished by fasudil as well as statin. Expression of NOX4 mRNA (catalytic subunit of NAD(P)H oxidase) was up-regulated in the renal cortex of diabetic rats, an effect which was also abolished by fasudil as well as statin . The present study demonstrates that the Rho/Rho-kinase pathway is involved in up-regulation of TGF-β, CTGF and NAD(P)H oxidase in diabetic kidney. We conclude that suppression of the Rho/Rho-kinase pathway could be a new strategy for the treatment of diabetic nephropathy.

Tissue kallikrein reverses insulin resistance and attenuates nephropathy in diabetic rats by activation of phosphatidylinositol 3-kinase/protein kinase B and adenosine 5'-monophosphate-activated protein kinase signaling pathways.

We previously reported that iv delivery of the human tissue kallikrein (HK) gene reduced blood pressure and plasma insulin levels in fructose-induced hypertensive rats with insulin resistance. In the current study, we evaluated the potential of a recombinant adeno-associated viral vector expressing the HK cDNA (rAAV-HK) as a sole, long-term therapy to correct insulin resistance and prevent renal damage in streptozotocin-induced type-2 diabetic rats. Administration of streptozotocin in conjunction with a high-fat diet induced systemic hypertension, diabetes, and renal damage in rats. Delivery of rAAV-HK resulted in a long-term reduction in blood pressure, and fasting plasma insulin was significantly lower in the rAAV-HK group than in the control group. The expression of phosphatidylinositol 3-kinase p110 catalytic subunit and the levels of phosphorylation at residue Thr-308 of Akt, insulin receptor B, and AMP-activated protein kinases were significantly decreased in organs from diabetic animals. These changes were significantly attenuated after rAAV-mediated HK gene therapy. Moreover, rAAV-HK significantly decreased urinary microalbumin excretion, improved creatinine clearance, and increased urinary osmolarity. HK gene therapy also attenuated diabetic renal damage as assessed by histology. Together, these findings demonstrate that rAAV-HK delivery can efficiently attenuate hypertension, insulin resistance, and diabetic nephropathy in streptozotocin-induced diabetic rats.

Red Wine Prevents Brain Oxidative Stress and Nephropathy in Streptozotocin-induced Diabetic Rats

We have studied the effects of red wine on brain oxidative stress and nephropathy in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in Wistar rats with a single intraperitonally injection of STZ (50 mg/kg). Two weeks before and four weeks after injection, red wine was given orally in both normal and diabetic rats. Blood samples were taken from the neck vascular trunk in order to determine the glucose, triglycerides, total cholesterol, HDL-cholesterol (HDL-c), atherogenic index (AI), total protein, blood urea nitrogen (BUN), creatinine, insulin, lipid peroxidation products, reduced glutathione (GSH) and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. As well, we estimated the lipid peroxidtion, GSH and SOD, GSH-Px and catalase activities in brain and renal homogenates, and the excretion of albumin, proteins and glucose in urine over 24 h period. The administration of STZ caused significant increases in levels of glycosuria, proteinuria, albuminuria, glycemia, total cholesterol and AI, as well as in lipid peroxidation products in the brain, plasma and kidney, whereas it decreased the GSH content and SOD, GSH-Px and catalase activities. Treatment with red wine significantly prevented the changes induced by STZ. These data suggested that red wine has a protective effect against brain oxidative stress, diabetic nephropathy and diabetes induced by STZ, as well as it protects against hypercholesterolemia and atherogenic risk.

Renin, Prorenin and the Putative (Pro)renin Receptor

Renin is an aspartic protease that consists of 2 homologous lobes. The cleft in between contains the active site with 2 catalytic aspartic residues.1 Unlike other aspartic proteases such as pepsin or cathepsin D, renin is monospecific and only cleaves angiotensinogen, to generate angiotensin (Ang) I. Ang I is the precursor of the active end-product of the renin-angiotensin system (RAS), Ang II. Renin has also been called active renin to underline that an enzymatically inactive form of renin exists. In 1971, Lumbers found that amniotic fluid, left at low pH in the cold, acquired renin activity.2 Later, Skinner described a similar phenomenon in plasma.3 Acidification was not strictly necessary for this increase in Ang I-generating activity, because incubation at low temperature also increased renin activity, albeit to only 15% of activity after acidification. Soon it was postulated that this inactive, but activatable “big” renin (its molecular weight was 5 kDa higher than that of renin) was the biosynthetic precursor of renin. Hence, it was named prorenin. Only with the cloning of the renin gene in 1984 was prorenin definitively proved to be the precursor of renin.4 For reasons that are unknown, prorenin circulates in human plasma in excess to renin, sometimes at concentrations that are 100-times higher.5 Prorenin has also been demonstrated in plasma of cat, dog, cattle, pig, horse, sheep, rabbit, rat, and mouse. A 43-amino acid N-terminal propeptide explains the absence of enzymatic activity of prorenin. This propeptide covers the enzymatic cleft and obstructs access of angiotensinogen to the active site of renin. (Pro)renin is synthesized as a preprohormone. It contains a signal peptide that directs the protein to the endoplasmic reticulum and ultimately to the exterior of the cell. Both renin and prorenin can be fractionated into multiple species by isoelectric focusing. …

Streptozotocin-induced diabetic nephropathy in rats: The role of inflammatory cytokines

The role of inflammatory cytokines in the pathogenesis of diabetic nephropathy has been studied in streptozotocin-induced diabetic rats. Rat kidneys were examined by light and electron microscopy and kidney homogenates were also analyzed by Western blot and flow cytometry for the expression of markers of inflammation namely, CD4+ and CD8+ T cells, macrophages, MHC classes I and II, the proinflammatory cytokines tumor necrosis factor-α, interferon-γ and nitric oxide (NO). Light and electron microscope examination revealed infiltration of mononuclear cells throughout the renal parenchyma, with the glomeruli being more severely affected especially at 8 months after disease induction. Western blot and flow cytometric analyses revealed the infiltrating cells to be CD4+ T cells, CD8+ T cells and macrophages. Western blot analyses also revealed increased expression of the proinflammatory and Th1 cytokines tumor necrosis factor-α, interferon-γ as well as nitric oxide. Using flow cytometry, we have shown that the difference in expression of CD4+ T cells in control and diabetic kidneys is more significant at 1 month than at 8 months, while expression of CD8+ T cells is more significant at 8 months. We speculate therefore that diabetic nephropathy is probably initiated and driven by a Th1 process. CD8+ T cells, however, become more significant at later stages of the disease when tissue loss is evident. Since NO induction also occurs only after 8 months, we hypothesize that NO might be significant for the later stages of the disease. Our data implicate inflammation in the pathogenesis of diabetic nephropathy in view of the overexpression of the proinflammatory cytokines TNF-α and IFN-γ and the cells that secrete them in the early and late phases of the disease.

Protective effect of seed coat of azuki beans on nephropathy in streptozotocin-induced diabetic rats

Protective effect of seed coat of azuki beans on nephropathy in streptozotocin-induced diabetic rats

Effect of retinoic acid in experimental diabetic nephropathy

Although the pathogenetic mechanism of diabetic nephropathy has not been elucidated, an inflammatory mechanism has been suggested to contribute to its progression. Monocyte chemoattractant peptide (MCP)-1 attracts macrophages and T cells, and ultimately injures renal tissue. In early diabetic nephropathy, urinary excretion of MCP-1 was elevated, and increased as renal damage became more severe. Podocytes are expected to have an inflammatory role in diabetic nephropathy, as the surface expression of chemokine receptors such as CCR and CXCR on these cells has been recently reported. Although retinoid (retinal), a known anti-inflammatory agent, has been reported to be beneficial in some experimental models of renal disease, it has not been determined to prevent disease progression in diabetic nephropathy. We investigated the effects of all-trans retinoic acid on the production of MCP-1 under high glucose conditions in cultured mouse podocytes. We also evaluated whether all-trans retinoic acid inhibits inflammatory changes and improves renal function during the early stages of diabetic nephropathy in streptozotocin-induced diabetic rats. In cultured podocytes, high glucose stimuli rapidly upregulated the MCP-1 mRNA transcript and protein release. Treatment with retinoic acid tended to suppress the MCP-1 gene transcript, and significantly inhibited MCP-1 protein synthesis induced by high glucose stimulation. Urinary protein excretion and the urinary albumin : creatinine ratio (ACR) were significantly higher in diabetic rats 4 weeks after the induction of diabetes mellitus compared with control rats, and retinoic acid treatment markedly decreased both proteinuria and urinary ACR (proteinuria: 1.25+/-0.69 vs 0.78+/-0.72 mg/mgCr, P=0.056; urinary ACR: 0.47+/-0.25 vs 0.21+/-0.06 mg/mgCr, P=0.088). Urinary excretion of MCP-1 was rapidly increased 2 days after induction of diabetes mellitus in diabetic rats, and further increased until rats were 4 weeks of age, compared with control rats. Retinoic acid treatment resulted in 30% reduction of the urinary level of MCP-1 compared with vehicle-treated diabetic rats (119.3+/-74.2 vs 78.1+/-62.7 pg/mgCr, P=0.078). Immunohistochemistry revealed a significant increase in staining for MCP-1 and anti-monocyte/macrophage (ED-1) protein in the diabetic kidney, and retinoic acid treatment significantly suppressed intrarenal MCP-1 and ED-1 protein synthesis. In conclusion, podocytes are involved in the inflammatory reaction under diabetic circumstances, and these reactions were suppressed by retinoic acid. Retinoic acid also suppressed inflammatory changes in the diabetic rat kidney, and decreased proteinuria in diabetic rats. These results suggest that retinoic acid may have renoprotective effects in the early stages of diabetic nephropathy through an anti-inflammatory activity.

Mechanism of preventive effect of HMG-CoA reductase inhibitor on diabetic nephropathy

Previously, we have found that pravastatin prevents diabetic nephropathy in streptozotocin-induced diabetic rats independently of serum lipid levels. The aim of this study was to clarify the impact of pravastatin on the mesangial cells exposed to high glucose. Rat mesangial cells were cultured in DMEM containing low glucose (5 mM glucose), high glucose (25 mM glucose) and 25 mM glucose with 500 microM pravastatin for 48 hours, respectively. After harvesting, we examined membrane-associated Ras with immunoblot analysis, activity of mitogen-activated protein kinase (MAPK) in the cytosol fraction with in-gel kinase assay and expressions of TGF-beta mRNA with Northern blot analysis. Membrane-associated Ras, activity of MAP kinase, and expression of transforming growth factor-beta (TGF-beta) mRNA were increased in the mesangial cells cultured exposed to high glucose compared to low glucose. Pravastatin suppressed all these changes in membrane-associated Ras, MAP kinase and TGF-beta mRNA in high glucose. This study suggests that pravastatin suppresses the activity of Ras-MAP kinase cascade and induction of TGF-beta in the mesangial cells that have been exposed to high glucose.

Effects of Acute Ethanol Load on Development of Nephropathy in Streptozotocin-induced Diabetic Rats

Effects of Acute Ethanol Load on Development of Nephropathy in Streptozotocin-induced Diabetic Rats